An articulation is a symbol written above or below a note or chord which imposes a playing technique.
An accent indicates to strike a note to make it loud. Accents may be used to produce a irregular rhythmic pattern (metre).
Figure 1: Accents on two notes.
A staccato indicates to play a note for roughly half its time value.
Figure 2: Staccatos on two notes.
A tenuto indicates to play a note to its full time value, sometimes even longer.
Figure 3: Tenutos on two notes.
A wedge indicates to play a note for a quarter of its time value.
Figure 4: Wedges on two notes.
A marcato indicates to strike a note to make it loud, louder than an accent. Marcatissimo is the superlative.
Figure 5: Marcatos on two notes.
A staccatissimo has the same application as a wedge.
Figure 6: Staccatissimos on two notes.
A fermata indicates to pause on a note and prolong its duration.
Figure 7: Fermatas on two notes.
A short fermata prolongs the duration of a note or rest for shorter than a regular fermata.
Figure 9: Short fermatas on two notes.
A long fermata prolongs the duration of a note or rest for longer than a regular fermata.
Figure 8: Long fermatas on two notes.
An open/harmonic has various applications: for string instruments, it indicates that a natural harmonic is played; for brass instruments, the note is played open without lowering any valve or without mute; in organ notation, a pedal-note is played with the heel (when above the note, use right foot; when below the note, use left foot); and in percussion notation, the hi-hat is opened.
Figure 9: Open/harmonics on two notes.
A close/mute has various functions: for string instruments, it indicates to pluck a note with the fret-hand; for the horn, the note is stopped by placing the stopping-hand into the bell; and in percussion notation, the hi-hat is closed.
Figure 10: Close/mutes on two notes.
For string instruments, an upbow indicates to play a note with an upstroke.
Figure 11: Upbows on two notes.
For string instruments, a downbow indicates to play a note with a downstroke.
Figure 12: Downbows on two notes.
For string and keyboard instruments, an arpeggio is to play two or more notes ascending in a rapid succession with each note being sustained.
Figure 13: Arpeggios on two chords.
For string and keyboard instruments, an arpeggio up is to play two or more notes descending in a rapid succession with each note being sustained.
Figure 14: Arpeggio ups on two chords.
An arpeggio down has the same application as an arpeggio.
Figure 15: Arpeggio downs on two chords.
For wind instruments, a scoop is a gliss rising to the beginning of a note using the embouchure.
Figure 16: Scoops on two notes.
For wind instruments, a fall is a gliss falling from the end of a note.
Figure 17: Falls on two notes.
For wind instruments, a doit is a gliss rising from the end of a note.
Figure 18: Doits on two notes.
For wind instruments, a plop is a rapid gliss falling to the beginning of a note.
Figure 19: Plops on two notes.
Also see Ornaments | Noteheads.